Abrasive gun



Feb. 15, 1944.

N. J. QUINN ABRASIVE GUN 'Filed Feb. 3, 1943 6 Sheets-Sheet l Feb. 15, 1944.

N. J. QUINN ABRASIVE GUN Filed Fab. 3, 1943 6 sheds-sheet 2 Feb.-15, 1944. N. J. QUINN ABRASIVE GUN 7 Filed Feb. 3, 1943 6 Sheets-Sheet 3 1N VENTOR. NE! so- J JM QUINN BY 77M ATTORNEY.

Feb. 15, 1944. I NN 2,341,569

ABRAS IVE GUN Filed Feb. 3, 1943 6 Sheets-Sheet 4 INVENTOR s} NELSON J.' Qunw'v BY, E j wwmmfw ATTORNEY5 N. J. QUINN ABRASIVE GUN Feb. 15, l944.

Filed Feb. 3, 1943 s Sheets-Sheet 6 INVENTGR.

was

Patented Feb. 15, 1944 2,341,569 ABRASIVE GUN Nelson .1. Quinn, Toledo, Ohio Application February 3, 1943, Serial No. 474,498

15 Claims.

This invention relates to the art ofimpact cleaning or abrading wherein abrasive particles are forcibly projected against the surface being treated. More specifically, it relates to a method I and apparatus for throwing the abrasive in a rapid succession of separated charges or loads.

Apparatus heretofore widely employed by industry for abrading falls into three general types. The first type is tumbling" wherein a load of small castings and three-dimensional stars'are tumbled in a tumbling barrel so that the points of the stars abrade the castings. This type is suitable solely for small castings cut of material which does not readily fracture. The second type is an open air blast wherein abrasive constantly flows into an open air stream, a nozzle being provided for velocity and for directional control. The third type is a thrower wherein rotating blades throw the abrasive continuously fed thereto onto the work.

The continuous fiow of abrasive into an open air stream requires a great volume and extreme velocity of air to secure the desired results. The

rotating blade type has the disadvantage of requiring large, powerful and heavy apparatus, and which has limitations as to the kind 0 work it may do.

In the air blast type, the abrasive strikes the object to be cleaned or abraded at a speed which is low in comparison to the speed of the air stream and the density of the abrasive in the stream is very low. That is, a great volume of air is required to carry an exceedingly small volume of abrasive. The stream carrying the abrasive on striking the surface being treated tends to deflect the particles, lessening the effective striking angle.- The density of the air at the treated surface impedes the striking power of the abrasive particles.

In my pending application, Serial No. 364,931, filed November 8, 1940, are shown other forms of my present invention which have been used effectively to throw abrasive in separate mass-like bodies intermittently striking the surface with great rapidity and essentially at the most efiective angles and under their own momentum.

-The invention of the present application has been demonstrated to operate in the same general manner, but more effectively, and it has the advantages of longer life, more convenient replacement of the wearing parts, minimum efficiency in vibration and a higher degree of the use of the compressed air.

A specific object of the present invention is to provide an apparatus in the form of an abrasive gun for rapidly throwing comparatively dense charges of abrasive through a firing barrel, having a charge-holding breach, and in which-the means for supplying the abrasive to the breach may load the breach, cut off thesupply and close the breach during firing, all with a minimum of wearing movement. The breach is effectively closed against escape of air or abrasive under the firing pressure. An- I other. object is to provide a simple, effective mechanism for operating the breach-loading and closing mechanism and also to release an extremely short explosive blast of highly compressed air through the firing barrel and to effectively and instantly close 011 the air'from barrel, after discharge of the abrasive load.

Carrying out the present invention required solving a problem which has presented itself in many ways in the handling of moving abrasive. Cutting off and measuring from a supply stream of abrasive requires that some element pass through the stream, subjecting that element to constant abrasive wear. Any attempts to rapidly load and project abrasive from a given point or charge chamber by intermittent release of high pressure air has met with excessive wear on any moving parts cutting through the supp y stream.

Placing a slug or body of abrasive material into a discharge barrel and momentarily releasing air under pressure'to eject the same therefrom and of repeating the cycle rapidly, complicates the problem and adds another, namely, that of closing the charging opening against that pressure and preventing the pressure blowing back into the supply stream or conduit.

By my invention I am enabled to' eject the charge with great force in the shortest practicable time with the minimum escape of air from high pressure supply, and to coordinate the means controlling the air discharge after the filling or breach charging and in the instant' pleteness of the instantaneous closing of the barrel at the breach or charging opening, this means enables me to provide a commerclaily successful rapidly firing separate charge throwins The foregoing and further objects are accomplished in so effective a manner that great economies are attained. Fields of abrasive cleaning heretofore commercially prohibited, are opened. Present equipment may be used for a. much larger number of purposes, and several of my abrasive guns throwing much greater quantities of abrasive efiiciently and effectively may be used where one continuous stream of abrasive gun is now used and without an additional supply of air.

The rapidity of operation accomplishes the firing or discharging of the abrasive loads in such rapid succession as to compare with machine gun operation. The manner by which I have secured great durability, and ease of replacement of the parts subjected'to the greatest wear, will hereinafter appear. 7'

My present preferred and successful form of the invention is illustrated in the accompanying valves may be used, although, as'to all of these,

a fully operative successful structure is shown and will now be described in reference to the drawings.

In the drawings,

Figure 1 is a diagrammatic view of a firing barrel and breach closing element indicating what is believed to be approximately the condition of the abrasive charge as it leaves the barrel, in flight, and at the moment of impact.

Figs. 2, 3 and 4 are sectional views illustrating the movement between the barrel and closing eccentric roller showing the abrasive loading, the sections being taken approximately on a plane indicated by the line X-X of Fig. 5.

Fig. 5 is a fragmentary detail of the barrel and breach closing element showing the connectingoperating gear arrangement.

, Fig. 6 is a side elevation of the abrasive throwing gun assembly.

Fig. 7 is a top view of the same. Fig. 8 is a sectional detail illustrating the firing I barrel opening means.

Fig. 9 is a vertical sectional detail taken on a plane indicated by the line 9-9 of Fig. 6, showing the reciprocating element for oscillating the firing barrel.

Fig. 10 is a vertical axial section through the gun.

Fig. 11 is a horizontal sectional detafl through the barrel actuating piston cylinder and through the valve housing and air surcharge chamber.

Fig. 12 is a vertical sectional view through the feed discharge and barrel breach taken approximately on a plane indicated by the: line l2-i2' of Fig. 10.

1 Fig. 13 is an enlarged sectional detafl showing the loading position of the barrel and breach closing element.

Figs. 14, 15, 16 and 1'7 are sectional and fragmentary views of the valve control mechanism for reciprocating the barrel oscillating piston.

Figs. 18 and 19 are fragmentary vertical sectional views showing the firing valve and operating mechanism.

Fig. 1 is a schematic or diagrammatic illustration of the operation of my invention as carried out in my earlier application, above designated, and likewise shows the operation of the present invention. As there appears .8 is a firing barrel receiving a charge of abrasive A, through an opening in the side thereof. By a turning movement in cooperation with an eccentric platen-like roller C this opening is closed, and then a valve V is instantly opened and closed, releasing highpressure air behind the body of the abrasive charge. This valve and operating means should be capable of opening and closing so quickly that the abrasive charge is given time only to move well out of the barrel at a high rate of speed, and while the member C closes the charging opening in the barrel. Thus the abrasive is thrown in a mass or relatively dense assemblage of abrasive particles and is carried forward by its momentum by the force of the expanding air stream to the surface of the work-piece which is being cleaned or abraded, as. indicated at W. Three charges are shown in this view at Al, A2 and A3, and appear as expanding somewhat as they advance. The longitudinal expansion or bunching may vary considerably, but with a constant air pressureand a certain length of time of valve opening, the lateral expansion will be substantially uniform for any given distance between the barrel and the work-piece.

The degree of density of the charge and the spacing between the charges may vary. The arrangement herein shown and described may operate eflectively at 8 to 12 firings per second. The striking speed at 2-& ft. distance between the barrel and work, is estimated to be about 200 ft. per second. The charg clears out of the barrel cleanly and completely. The distance between the charges is not easily determined, but is perhaps a few feet up to 20 or 30 ft.

Charges striking the surface, thrown from a barrel efiect a high degree of abrasion, that is, they clear off or cut away a large amount of material from an area of 3 or 4 to 6 or 7 inches in diameter in a matter of a few seconds. Approximately 10 lbs. of steel grit may be thrown from such a tube with great effectiveness in about 15 seconds, and with the escape, or use, of but a few cubic feet of compressed air, measured at atmospheric pressure. ..Eflective and speedy operation of the firing air valve obviously affects this operation.

The turning of the barrel on its axis beneath a chute or guide for the material, indicated 'at H, Figs. 2, 3- and 4, permits the material to flow into the barrel as its opening moves to full-open or closing of the supply stream.

When the supply is cut oil, the closing element C has been moved into the-filling opening, effectively closing,the same, as shown. At this same instant, a connecting mechanism opens the air valve and air pressure behind the abrasive charge is released against it, and then is instantly closed. A few cubic inches of compressed aironly is needed to forcibly eject the charge. In a cycle of tenshots per second, I have computed and estimated byvarious methods that the firing air valve is fully opened and closed in an interval of '{)"'to 5 of a. second. The balance of the timegof about 1 6 of a second for each'firring cycle, is allowed for the filling or loading.

Reciprocating turning motion of the barrel brings its loading opening into full registration with a supply stream from a chute H. The barrel shuts off that stream as it returns from open position (Fig. 4) to closed position (Fig. 2). Likewise this return movement closes the breach opening 0 of the barrrel.

' The length of and width of this loading slot 0 in the barrel may be varied,- of course. I have found that in a barrel, the filling opening may be 2 to 4 inches long and to ft" wide. The closing roller may be a cylinder of fairly stiff rubber or like resilient material, preferably extending the full length of the opening and its diameter is preferably from A to larger than the outside diameter of the barrel.

It is shown as mounted slightly above the cen-' ter of the barrel and is eccentrically and rigidly carried on its shaft S and geared to the barrel, preferably at both ends as by gears G.

In operation an important result of such an arrangement, is that as the barrel moves to the filling position, the surface of the roller tends to expand and facilitates the quick opening with a minimum friction.

1 tion the edge of the opening toward the roller presses into the roller somewhat for a brief portion of the swing, thus depressing the roller to the greatest depth of such depressing action, as the edge, that is the lower edge in Figs. 2 to 4, passes the line L between the axes of the barrel and shaft S. The resiliency of the roller itself in the'further movement of this edge minimize power required to complete the closing. The closing is completed before the axis of the closing roller, reaches the plane through the axes of the barrel and shaft S. Thus the final closing pressure is in the nature of a toggle action, as shown by the dot and dash force lines Li in Fig. 2, forcing the roller surface very tightly into closing position. Thus the firing air pressure is effectively confined and neither air or abrasive escapes at the moment of firing.

It will also be seen that the opening movement draws the upper edge of the barrel opening 0 away from the loose falling material. -This motion is with a minimum of abrasive action.

The same upper edge cuts across the loose falibe ordinary steel tubin although preferably it is of hardened material. It. is obviously a relatively cheap part to be replaced. Other parts of the abrasive throwing gun are protected from abrasive wear, and may have a life of operation comparable to that of commercial pneumatic hammers and similar pneumatic tools.

In the particular construction the barreland roller should be journalled in rigid supports at opposite ends. These supports may be transverse walls of a suitable housing, which may contain the abrasive chute, and to whichmay be attached the mechanism for oscillating the barrel and roller and for controlling or operating the valve for the firing charge of compressed air. For the purpose of this application, the drawings show such an arrangement which has been successfully operated.

In'the arrangement shown the gun comprises essentially a housing 7.5 for the abrasive chute and barrel and closure operating mechanism; at the rear end of this housing is a housing for the air valve operating mechanism and barrel oscillating means indicated at 21. 28 shows an extension which houses the air valve opening mechanism and constitutes in effect an air reservoir sur rounding the air valve as will presently appear.

The housing 25 may be of any suitable construction, but as shown it comprises lower and upper half-cylinder members 30 and 3|. The lower is rigidly secured to end wall disc 32 at one end and 33 and 34 at the other. The upper half-cylinder housing member is desired to be readily removable and may be fitted between the rigidly supported disk members and into the lower half, forming a tight chamber. From the upper hous ing member 3| a feed pipe 3'! rises, as showmand may be connected to any suitable supply chamber for feeding abrasive to the gun.

The firing barrel 26 preferably extends a substantial distance forwardly to the housing and through end wall members of the housing into the air chamber member 28. The feed chute 42 within the housing is preferably carried between two disc supports 41, affording additional journals for the bearing of the barrel and for the shaft 45 of the closure member C. The gearing heretofore designated generally G in reference to Figs. 2 to 5, inclusive, preferably comprises a tooth segment 4B engaging teeth 48 formed in sleeves 49, rigid with the barrel either side of the opening 0 and outside of the discs 4!, whereby the gears are protected from the grit in the chute and at the breach loading position.

In order that the rolling action between the closure 0 and the barrel B will be free from relative slipping and consequent friction and loss of power, I find it desirable to arrange the gear teeth on the .barrel and the segment 46 so that the pitch line of the gears is in one case coincident with the barrel and in the other, of course, tangent thereto. Although the surface of the closure C is not coincident with the pitch circle of the gear segment 46, it approaches this coincidence when the barrel opening 0 and closure 0 are in the full open position as in Figs. 4 and 13. It will be found that this is consistent with the requirements above indicated, that grit be prevented from getting between the surface of the barrel and the surface of the closure.

The shape of the closure C may be, of course, varied. It may be-a segment in cross-section not unlike the gear sector 46, or it may be a sector of a cylinder, the axis of which is coincident with the carrying shaft, however, the advantages indicated prove the value of an arrangement approximately as shown.

Another advantage of this arrangement is that as the barrel and closure turn from the position of Fig. 4 back through a position such asFig. 3 to the closed position, Fig. 2, the surface of C engages a body of falling grit, actually pressing or pushing it into the barrel, assuring a uniform loading with each movement. At certain speeds this loading may be timed to permit the substantial filling of the barrel for a distance the length of the opening 0 and the material may be somewhat packed or pressed into position. However,

with only a partial filling, but, again as the feed stream is being cut off, as at'the position Fig. 3, with the barrel turning toward closed position, the bulging surface of ,C opposite the opening wipes downwardlyand inwardly as the feeding is cut off, shoving the material in front of the surface of C and into the barrel opening. Thus the speed of falling is of less consequence it it varies somewhat than as though the closure of the opening were effected by simple rolling action as between the rolling of a clothes wringer, for example.

Incidentally, a cylinder-type closure roller with the bulging portion to feed into an opening of the barrel has been operated but requires more power and is less effective than the arrangement shown.

To oscillate the barrel and closure C, I may apply power to either the barrel or shaft 45. In the arrangement shown power is applied first to the barrel through a hub 55 removably screwed thereto as by a thumb screw and pin indicated at 60 and for an arcuate extensions 56 rigid therewith, the ends of which may fit between flanges 69 on a double piston member 68 having piston heads 61 operating in opposed cylinders 65 and to which air pressure is alternately applied from the common source of pressure supply. A threaded plug 38 permits the assembly of the piston and barrel actuating segment 56 by inserting a double piston from one end of the opposed cylinder housing. Any suitable valve mechanism may control the actuation of the double piston which, in effect, operates similar to a windshield wiper. A satisfactory mechanism of this nature is described,

Figs. 14 to 17.

It is obvious, however, that any method of applying oscillating motion to either the barrel or the shaft, as for example, by a rotary motor with link connection of the oscillating member, or electric motor with oscillating connections such as used in many cases, for example, in washing machines, have proven satisfactory.

s The detail ofsecuring the member 55 to the barrel head in turn may actuate an air valve tripping and controlling device shown particu-- larly in Figs. 18 and 19. Referring to Fig. 8, the member 55 is tightly fitted over the barrel and the pin 59 extends through a suitable lock nut and is shown as covered by a cap'60 with an opening 6| for a screwdriver to engage the slotted and threaded head 50 through the pin 59. On the opposite side of themember 55 iS a projecting pin 53 engaging one arm of a bell crank I rigid with the shaft |0| the other arm I02 of the first bell crank and a like single arm I03 rising from the shaft engage valve tripping pins I05 and I06 extending through the wall of the housing 21 and into the air chamber 28. The member I06 is shown as extending through the carrier sleeve I I0 for the air valve II 2' or V as heretofore described, and also through a pin II5 having air grooves IIB controlling the movement of thevalve operating piston I20.

Th piston I20 is mounted in a rigid cylinder I25 and has a tubular extension I30 threaded to the rear wall of the housing chamber 23. By loosening a locking nut I3I the extension I30 may be screwed inwardly or outwardly, changing the position of the cylinder I25 and valve V for adjustment toward or away from the firingtube and for thus regulating the. amount of the .valve opening. This adjustment also not only affects the amount of air. which may be released, but by it the time during which the valve is at higher speeds the gun may be more efiective opened, may be increased and decreased slightly.

As the barrel oscillates from open to closed position, pin 53 rocks the arm I00 and in turn the arms I02 and I03 to move the pin 5 within the carrier sleeve IIO shown as slotted II3 to permit this movement. The first inward movement of the valve pin II5 causes the communicating slot IIB to connect the openings III and I I1, admitting air to the forward side of the piston I20. The piston and valve carrier 0 being rigid, this serves to instantly move the piston rearwardly carrying valve V with it, opening the valve from the position of Fig. 18 to that of Fig. 19. Now the groove or slot H9 which closed the opening 8 in the position shown in Fig. 18, opens the vent II8. Air passes through the vent H8, vent groove II9 to the space behind the piston where it may exhaust through the openings I29 to the open air. Thus the air pressure on both sides of the piston I20 is equalized and the action of the springs I21 and I28'instantly closes the valve V. They are of such size as to release the pressure behind the piston during the interval of the loading and closing of the barrel so that a new thrust on the valve pin I I5 will renew the air pressure in front of the piston I20, the rearward thrust of thevalve pin II! through the members I05 and I06 and bell crank arms I00 and I02 and pin 53 will again cause instantaneous opening of the valve V, whereupon the cycle is repeated, Referring to Figs. 14 to 17, a suitable control mechanism for delivering the air alternately to opposite ends of the double piston 61 may comprise a rock shaft ll with a sector abutment positioned between the operating abutment flanges 69, which also act on the arcuate segment 56 to rock the barrel. In Fig 11 one abutment has turned this sector 18 turn ing the shaft 11 so that a valve plate 85 carried thereon is connected to air duct 82 from the upper cylinder with the exhaust duct 8|, at the same time this opening duct 83 leading to the lower cylinder.

Air under pressure is supplied to the chamber indicated at II and this pressure air acts to move the piston upwardly until the sector abutment 18 rock shaft and valve plate 85 are moved to connect the duct 83 with the exhaust and in turn open 82 to the pressure air.

A snap-over toggle is preferably provided to secure quick opening and closing ducts by corresponding quick full movement of the plate 85. For this purpose a plate 95 also rigid on the rock shaft 11 is shown as having a slot or bifurcated opening 88 engaging the end of pivotedthrow lever 90 mounted on a pivot pin 9| and the tension spring '93 extending between the anchor members 92 on the plate 30 and the pin 94. on the plate 95 is alternately thrown from one side to the other of the center line between shaft 11 and pivot 9|. The result is that as the abutment sector starts to turn it need only move until the 4 spring passes its neutral position to cause it to snap the members 90 and. 95 to the opposite extreme position, correspondingly quickly moving the valve plate 85; as heretofore stated, this valve control and piston arrangement for actuating the barrel and closing mechanism and in turn also actuating the valve opening piston, may .be any suitable construction and may be acted upon by air from the same source of supply as the air which throws the material out of the firing barrel, or may be separate fluid or electric motor as good design, shop practice and intended use may require. I

The valve V is shown as a disk which is preferably somewhat resilient and as fitting tightly upon the smoothly finished inner end of the barrel B. Here again this construction may be varied and instead of a valve carried bodily by this actuating piston, quickly actuated closure valves of types'known in other pneumatic tools, may be used.

The essential objectives heretofore stated being to efliciently operate the barrel charging and closing means and to quickly, fully and widely open an air valve to thepressure supply and instantly close after the discharge of the abrasive and before the barrel and closure begin to separate for the next opening movement,

The supply of air may be small in volume compared to the amount of material to be thrown, when considered in the light of previous air blast practice, however, effectiveness-of the discharge giving an explosive-like action of the pressure air and is aided by the chamber, as at 28, to

which the air supply is led through a pipe, as indicated at 33. Thus a few cubic inches, preferably suillcient for the discharge is stored under full pressure, immediately surrounding it next to the air valve, thus eliminating any delay in flow or drop in pressure for the single discharge. The discharge time being. only a fraction of the loading time, obviously the explosive air supply chamber may have ample time to be refilled.

In the arrangement shown, air may be supplied through a pipe H connected to the same source, preferably some distance away from the gun by a tube, indicated at M, leading to the chamber 1 l. I

It may be connected with the valve mechanism said opening and at the same time to cause the barrel to close the supply chute, and-means for releasing compressed air through the barrel when said opening therein is closed.

2. An abrasive gun for rapidly throwing separate dense charges of abrasive and having a firing barrel with an opening forming a charging breech, a supply means causing abrasive tomove into said opening, means for moving the barrel to shut oil the supply means, means correlated with said movement for closing the breech open- 2 ing, and a coacting responsive means for releasas accessibility for cleaning and repair through the removable cover indicated at I5, on the housing H. The main air valve mechanism is likewise accessible by' reason of the threaded gun and lock nut screwing means for adjusting the pressure and opening distance of the valve as indicated at Mt. The piston carrying hollow stem being threaded into the wall of the housing at a boss TL I From the foregoing description it will .be seen that the operation of loading a firing 'bah'rel through a lateral opening and closing it with a rolling resilient member, while effectually cut-. ting oil. a s pply stream, may be carried out by comparatively simple mechanism capable of being assembled in a convenient housing structure, which maybe portable or stationary and have many advantages, including, all those herein 7 may be uniformly closed or may be left open, and any overflow or leakage occurring may be accumulated in a suitable receptacle I50, Fig. 10.

Having thus described my invention, what I claim is:

1. In an abrasive firing gun, a barrel having a lateral breechopening, a resilient rolling member for closing said opening, an abrasive supply conduit leading to the barrel, a means for relatively moving the barrellclosure and supply means to alternately register the opening with .the supply conduit and to bring the closure over 75 8. an abrasive throwing gun ing a charge of compressed air through the barrel only while the breech is closed.

3. An abrasive gun for rapidly throwing separated charges of abrasive, having a firing barrel with a lateral breech opening therein, a supply conduit and means for closing the breech opening, operating means connecting the barrel and closing means forcausing relative movement between the barrel and the supply means and closing means to bring the opening into registration with the supply means and thereafter to close the supply means and breech opening, and means for releasing compressed air through the barrel when the breech opening is closed.

4. An abrasive throwing gun for rapidly throwing separate dense charges of abrasive, having a firing barrel with a charging opening in the side thereof, a supply chute'for bringing abrasive to the opening, a closure member cooperating with the barrel, means for turning the barrel with relation to the supply chute to shut oil the supply chute and present the opening to the closure member, and means for releasing a charge of compressed air through the barrel when the breech opening is closed.

5. An abrasive throwing gun adapted to forciblythrow dense charges of abrasive intermittently in rapid succession, and having an oscillating barrel with an opening therein, a supply chute leading to the opening when in one position and a resilient roller contacting the barrel and closing the same when the barrel moves to another position, the side of said barrel 010s ing the supply chute when its loading opening close the opening as it moves away from the .;,rore it can flow to repose.

chute, the barrel being arranged to close the end of the chute when the banrel is moved to the position closing its charging opening, and interconnected synchronized means for releasing the charge of air through the barrel when its charging opening is closed.

7. Anabrasive gun for rapidly throwing separate charges of abrasive, having a firing barrel ,with an opening forming a charging breech, a supply means leading abrasive into said opening, means for moving the barrel to shut oil? the supply means, n ieans responsive to the barrel movement for closing the breech opening, and a coacting responsive means for releasing a charge or compressed air through the barrel only while the, breech is closed and with such rapidity that the abrasive within the barrel is discharged behaving an I- lating barrel with a lateral charging opening, a chute leading to the barrel for bringing abrasive to the opening when the barrel is moved to one position, a roller member adapted to close the opening when the opening is moved away from the chute, the barrel being arranged to close the end of the chute when it is moved to the position closing the charging opening, and interconnected synchronized means for releasing the charge of air through the barrel when it is closed and with such rapidity that the abrasive is not given time to fall and flow to a position of mass repose within the barrel, or to flow out of the muzzle.

9. An intermittently firing abrasive throwing gun, a barrel having a side loading opening, a chute leading thereto, the side of the barrel being arranged to close the chute, means for oscillating the barrel from the closed to open position, an eccentric roller contacting the barrel adjacent to chute and acting to close the opening and prevent escape to abrasive when the chute is closed, a source of air pressure and a valve for admitting such air to the barrel, a means for opening the valve instantly upon the closing of the loading opening and said means permitting the valve to close immediately upon the air discharging the abrasive from the barrel, the time of the valve opening being a small fraction of the time required for the loading and closing movement of the barrel.

10. An abrasive throwing gun having 'a barrel and an oscillating breech opening, a chute leading abrasive to the inside of the barrel through the breech opening, an eccentrically mounted roller adapted to register with and close said opening with a toggle pressure action, and means for discharging air through the barrel to throw out the abrasive only when the breech opening is closed.

11. An intermittent rapid firing abrasive gun, having a barrel provided with a charging breech, an abrasive conduit leading thereto, and coactin oscillating elements, one of which presents an eccentrically mounted resilient surface to close the breech opening when in one positionand which moves bodily away from the opening as the latter is moved to register with the conduit, a source of air supply, a control valve therefor, and means for opening the control valve only when the breech opening is closed, said eccentric resilient surface acting in its movement to contact the barrel to prevent abrasive falling between said surface and the barrel and when closing to push a portion of abrasive stream into the barrel while the barrel cuts oil the chute opening and also acting to close the opening with a toggle action pressure.

- 12. An abrasive gun for rapidly throwing separate dense charges of abrasive and having a firing barrel, intermittent air releasing means for discharging the abrasive from the barrel, means for loading abrasive into-the barre1 including a having an open discharg end and a side charging opening, a roller closure for said charging opening, an abrasive carrying chute positioned-to be closed by the side of the receptacle and to register with the charging opening, mean for causing relative movement between the receptacle and chute and roller closure to alternately open and close the chute and the charging opening, and means for emptying the barrel of abrasive by fluid pressure when the charging opening is closed.

14. An abrasive handling device having in combination an oscillating barrel having an open end and a side opening, an abrasive carrying chute positioned to be closed by the side of the barrel and to register with the side opening, a resilient roller closure member engaging with the barrel for closing the side opening, the oscillating move- I ment of the barrel acting to alternately bring the side opemng into-registration with the chute, and the closure, and an intermittently operative fluid pressure means for ejecting abrasive from the barrel when the side opening is closed.

15. An abrasive throwing apparatus, comprising an oscillating barrel having a side opening, an abrasive carrying chute arranged to register with the side opening and to be closed by the side of the barrel, a resilient roller closure contacting the barrel and rolling with it to close the side opening, co-acting gear teeth between the roller and barrel to govern such movement and havin their pitch lines tangent approximately at the barrel surface, a fluid pressure supply, a valve for releasing pressure fluid through the barrel, and an operating means for the valve actuated by the barrel and roller closure movement.

- NELSON J. QUINN. 

